Use TaskScheduler instead of WorkerPool in trace_log.cc.

Use TaskScheduler instead of WorkerPool in trace_log.cc.

The following traits are used to post a task to TaskScheduler:

.WithPriority(TaskPriority::BACKGROUND)
  User won't notice if this task takes an arbitrarily long time to
  complete.

.WithShutdownBehavior(TaskShutdownBehavior::CONTINUE_ON_SHUTDOWN)
  Tasks posted with this mode which have not started executing before
  shutdown is initiated will never run. Tasks with this mode running at
  shutdown will be ignored (the worker will not be joined).

  Note: Tasks that were previously posted to base::WorkerPool should
  use this shutdown behavior because this is how base::WorkerPool
  handles all its tasks.

.MayBlock()
  Tasks with this trait may block. This includes but is not limited to
  tasks that wait on synchronous file I/O operations: read or write a
  file from disk, interact with a pipe or a socket, rename or delete a
  file, enumerate files in a directory, etc. This trait isn't required
  for the mere use of locks.

BUG=659191
Review-Url: https://codereview.chromium.org/2675273002
Cr-Commit-Position: refs/heads/master@{#448248}
Committed: https://chromium.googlesource.com/chromium/src/+/cdab762270b332aeb4c38f31d2a97720665fdf1d

[fdoray, 2017-02-06 10:53:27]

The CQ bit was checked by fdoray@chromium.org to run a CQ dry run

[commit-bot: I haz the power, 2017-02-06 10:53:44]

Dry run: CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[fdoray, 2017-02-06 10:55:23]

The CQ bit was checked by fdoray@chromium.org to run a CQ dry run

[commit-bot: I haz the power, 2017-02-06 10:55:43]

Dry run: CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[commit-bot: I haz the power, 2017-02-06 12:07:46]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2017-02-06 12:07:47]

Dry run: This issue passed the CQ dry run.

[fdoray, 2017-02-06 13:31:12]

fdoray@chromium.org changed reviewers:
+ dsinclair@chromium.org

[fdoray, 2017-02-06 13:31:13]

PTAL

[dsinclair, 2017-02-06 14:23:40]

lgtm

[Primiano Tucci (use gerrit), 2017-02-06 14:55:34]

> User won't notice if this task takes an arbitrarily long time to complete.
This is not really true. We had a similar instance happening in crbug.com/675735
where due to purge&suspend + timer throttling chrome://tracing was taking
O(minutes) to start/stop and that was annoying for users.

[fdoray, 2017-02-06 14:55:36]

The CQ bit was checked by fdoray@chromium.org

[commit-bot: I haz the power, 2017-02-06 14:55:46]

CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[commit-bot: I haz the power, 2017-02-06 14:59:35]

CQ is committing da patch.

Bot data: {"patchset_id": 40001, "attempt_start_ts": 1486392936649220,
"parent_rev": "9b0eabfd75abb590b52f2d18b5afaea6ffefac8b", "commit_rev":
"cdab762270b332aeb4c38f31d2a97720665fdf1d"}

[commit-bot: I haz the power, 2017-02-06 15:00:07]

Description was changed from

==========
Use TaskScheduler instead of WorkerPool in trace_log.cc.

The following traits are used to post a task to TaskScheduler:

.WithPriority(TaskPriority::BACKGROUND)
  User won't notice if this task takes an arbitrarily long time to
  complete.

.WithShutdownBehavior(TaskShutdownBehavior::CONTINUE_ON_SHUTDOWN)
  Tasks posted with this mode which have not started executing before
  shutdown is initiated will never run. Tasks with this mode running at
  shutdown will be ignored (the worker will not be joined).

  Note: Tasks that were previously posted to base::WorkerPool should
  use this shutdown behavior because this is how base::WorkerPool
  handles all its tasks.

.MayBlock()
  Tasks with this trait may block. This includes but is not limited to
  tasks that wait on synchronous file I/O operations: read or write a
  file from disk, interact with a pipe or a socket, rename or delete a
  file, enumerate files in a directory, etc. This trait isn't required
  for the mere use of locks.

BUG=659191
==========

to

==========
Use TaskScheduler instead of WorkerPool in trace_log.cc.

The following traits are used to post a task to TaskScheduler:

.WithPriority(TaskPriority::BACKGROUND)
  User won't notice if this task takes an arbitrarily long time to
  complete.

.WithShutdownBehavior(TaskShutdownBehavior::CONTINUE_ON_SHUTDOWN)
  Tasks posted with this mode which have not started executing before
  shutdown is initiated will never run. Tasks with this mode running at
  shutdown will be ignored (the worker will not be joined).

  Note: Tasks that were previously posted to base::WorkerPool should
  use this shutdown behavior because this is how base::WorkerPool
  handles all its tasks.

.MayBlock()
  Tasks with this trait may block. This includes but is not limited to
  tasks that wait on synchronous file I/O operations: read or write a
  file from disk, interact with a pipe or a socket, rename or delete a
  file, enumerate files in a directory, etc. This trait isn't required
  for the mere use of locks.

BUG=659191

Review-Url: https://codereview.chromium.org/2675273002
Cr-Commit-Position: refs/heads/master@{#448248}
Committed:
https://chromium.googlesource.com/chromium/src/+/cdab762270b332aeb4c38f31d2a9...
==========

[commit-bot: I haz the power, 2017-02-06 15:00:08]

Committed patchset #3 (id:40001) as
https://chromium.googlesource.com/chromium/src/+/cdab762270b332aeb4c38f31d2a9...